There are disclosed herein photoconductors containing a hole blocking layer or undercoat layer (UCL) comprised, for example, of metal oxide particles and a silanol. More specifically, there are disclosed herein a hole blocking layer comprised of metal oxide particles, a silanol, and polymeric resins. Even more specifically, there are disclosed herein hole blocking layers comprised of a number of the components as illustrated in the copending applications referred to herein, such as a metal oxide like a titanium dioxide, a polyol resin, and an aminoplast resin, such as a melamine resin, and wherein the metal oxide is treated with a hydrophobic silanol by, for example, the in situ modification of the metal oxide surface to form silanol hydrophobic moieties thereon. Also, in embodiments the metal oxide hole blocking layer component, such as titanium oxide nanoparticles, can be pretreated with hydrophobic silanols and subsequently dispersed in a polymeric binder thus resulting in the formation of the undercoat layer. Alternatively, the silanols can be simply added to the hole blocking layer dispersion.
Although not being desired to be limited by theory, it is believed that the silanol groups attach to the metal oxide rendering it hydrophobic, and wherein the remaining amount of the silanol interacts with the polymeric binder allowing the metal oxide pigment to be readily dispersible. The silanol is believed to also stabilize the hole blocking layer dispersion thereby minimizing dispersion aging effects that increases ghosting because of pigment re-aggregation.
In embodiments, a photoconductor comprised of a silanol hole blocking or undercoat layer enables, for example, minimal print quality failure, such as charge deficient spots (CDS) caused by the humidity sensitive metal oxide that, for example, is more conductive in humid environments. Moreover, in embodiments there are provided photoconductors with a number of acceptable characteristics, such as excellent adhesion of the UCL to layers thereunder and thereover thus avoiding or minimizing delamination; minimizing or substantially eliminating ghosting; and permitting compatibility with the photogenerating and charge transport resin binders, such as polycarbonates. Charge blocking layer, and hole blocking layer are generally used interchangeably with the phrase “undercoat layer”.
Also included within the scope of the present disclosure are methods of imaging and printing with the photoresponsive or the photoconductive devices illustrated herein. These methods generally involve the formation of an electrostatic latent image on the imaging member, followed by developing the image with a toner composition comprised, for example, of a thermoplastic resin, colorant, such as pigment, charge additive, and surface additives, reference U.S. Pat. Nos. 4,560,635; 4,298,697 and 4,338,390, the disclosures of which are totally incorporated herein by reference, subsequently transferring the image to a suitable substrate, and permanently affixing the image thereto. In those environments wherein the device is to be used in a printing mode, the imaging method involves the same operation with the exception that exposure can be accomplished with a laser device or image bar. More specifically, the imaging members, photoconductor drums, and flexible belts disclosed herein can be selected for the Xerox Corporation iGEN3® machines that generate with some versions over 100 copies per minute. Processes of imaging, especially xerographic imaging and printing, including digital, and/or high speed color printing, are thus encompassed by the present disclosure.
The imaging members disclosed herein are in embodiments sensitive in the wavelength region of, for example, from about 400 to about 900 nanometers, and in particular from about 650 to about 850 nanometers, thus diode lasers can be selected as the light source.